Alien Submarines

The USOs used by the aliens are big, blocky, shapes which resemble sea creatures and lack most forms of aerodynamics. They are able to dive and fly at breakneck speeds through the power of Zrbite and the resiliency of Aqua Plastics. USOs come in a variety of forms ranging from the tiny Survey Ships right up to the massive Dreadnoughts.

USOs are the aliens' sole method to move around Earth, and collect resources, so in theory, it would be possible to halt the alien advance if X-COM could maintain absolute naval superiority. Earth's forces do not initially have the resources required for such a task, and even if it becomes possible, the aliens have an vast resource supply and will not be set back by a war of attrition. In addition, alien undercover agents will continue to erode Earth's defenses from the inside.

Despite this, commanders should still down as many USOs as possible. At the very least, it may slow the aliens down some.

UFO Types

The aliens use special submerging vehicles known as USOs. The USOs deployed by the aliens range in size and the mission profiles they are most commonly seen on, some are also much more common to certain of the alien races encountered.

Very Small UFOs

Survey Ship - Very Small USO. Primarily used for research.

Small UFOs

Escort - Able to fill a variety of roles.

Cruiser - Slightly larger than the Escort. Very versatile.

Medium USOs

Heavy Cruiser

Hunter

Large USOs

Fleet Supply Cruiser - Large-sized USO for tranportation of aliens, food, and other supplies.

Battleship - Large USO used to unleash assault teams and Terror Units on residential areas.

Very Large USOs

Dreadnought - Very Large USO used to intimidate Earth's peoples and leaders, and to assault X-COM bases, along with a variety of other roles.

Quick Comparision Table

>>>>>>>>>>>>>>>>

Craft	Size	Max Speed	Weapon Power	Weapon Range*	Damage Capacity	USO Downed Points	USO Destroyed Points
Survey Ship	Very Small	2,000	0	0	60	50	100
Escort	Small	2,800	30	104	300	75	150
Cruiser	Small	2,600	25	280	300	125	250
Heavy Cruiser	Medium	3,800	60	160	450	250	500
Hunter	Medium	4,500	50	144	500	250	500
Fleet Supply Cruiser	Large	3,400	70	304	2000	400	800
Battleship	Large	4,200	120	400	1400	500	1000
Dreadnought	Very Large	4,800	140	480	3400	700	1400

* The figures given in the in-game UFOpaedia are a factor of 8 too high, relative to Sub Armament ranges.

Weapons vs. USOs

Comparing the weapon range and damage capacity of UFOs to the range and damage of Sub Armaments, one can discern that:

• Any weapon, even the lowly Craft Gas Cannon, can be used against Survey Ships, since they can't shoot back.
• AJAX Torpedoes, with a range of 32km, are completely safe to use against Escorts, and can even be used to safely down Heavy Cruisers and Hunters.(Shouldn't the Heavy Cruiser be better than the Cruiser? Oh well...)
• D.U.P. Head Torpedoes or Sonic Oscillators should be used against Cruisers due to their weapon range of 35km.
• D.U.P. Head Torpedoes can fire on all but the Battleship and Dreadnought with impunity.
• Gauss Cannons, with a range of 20km, can be safely used against the Survey Ship, Escort, and Hunter. However, D.U.P. Head Torpedo-armed craft are of use against a larger variety of craft and Sonic Oscillators, once they become available, are superior in every regard.
• Sonic Oscillators can safely be used (even by Barracudas) against any USOs except Dreadnoughts. Even against Dreadnoughts, Sonic Oscillators are better than P.W.T. Launchers because a minimum of four P.W.T.-armed craft are required to down a Dreadnought.

Subs vs. USOs

• The Barracuda can always be used effectively against Survey Ships, for the Barracuda is faster.
• The Manta is faster than all USOs EXCEPT the Dreadnought.
• The Hammerhead can intercept all USOs except the Hunter, the Battleship, and the Dreadnought, which must slow down in order for the Hammerhead to catch up.
• The Leviathan is 1000 speed units faster than even the mighty Dreadnought and can intercept all alien USOs.